Cellulase in the host-parasite system Phaseolus vulgaris (L.) - Uromyces appendiculatus [Pers.] Link

Activity of cellulase and xylanase in the intercellular washing fluid (IWF) of bean plants (Phaseolus vulgaris, cultivar Fori) was monitored during in fection with bean rust (Uromyces appendiculatus). In infected plants, cellu lase activity could be detected at 2 days after inoculation and reached its maximum between 7 and 8 days after inoculation. The enzyme activity was no t detected in healthy controls. The cellulase had a pH optimum at pH 5.5 an d a temperature optimum at 30 degrees C. Complete inactivation of cellulase occurred after heating to 50 degrees C for 30 min. In non-denaturing polya crylamide gradient gels, the enzyme exhibited four bands (molecular masses approximately 70, 95, 120, 170 kDa). After isoelectric focusing, eight cell ulase isoforms with pI values pI 4.6-4.8; 5-5.1; 5.4; 5.5; 5.9; 6; 6.5; 7 a ppeared. Two dimensional electrophoresis yielded 13 cellulase isoforms. Unl ike cellulase, low levels of xylanase were detected in healthy controls. Th e activity of this hydrolase did not increase due to rust infection.